Color Doppler and Duplex Doppler US were employed on 4 patients with clinically suspected pseudoaneurysms as a complication of femoral artery puncture after cardiac catheterization. Pseudoaneurysms were identified with Color Doppler US and their typical appearance was confirmed. The grey-scale findings did not allow an adequate differentiation between hematoma and pulsed hematoma without fibrous encapsulation: only Color Doppler US easily detected the track between damaged artery and blood collection and allowed a sample to be obtained for pulsed Doppler examination. Color Doppler US allowed an accurate and non-invasive diagnosis of groin masses after femoral artery catheterization.